Worn insulation lets a short circuit form across 240-V AC through a resistance of just 0.250 ohm. How much power is dissipated in the short?

1. A short circuit is a low-resistance path across a voltage source, so use P = V squared / R. 2. Square the voltage: 240 V x 240 V = 57,600 V squared. 3. Divide by the resistance: P = 57,600 / 0.250 ohm. 4. This gives P = 230,400 W. 5. Convert: P = 230 kW, enough thermal power to melt or ignite the surroundings almost instantly. 6. 57.6 kW is the trap of forgetting to divide by the 0.250-ohm resistance, and 23.0 kW shifts the decimal one place. 7. 960 kW mistakes the current (240 / 0.250 = 960 A) for the power in kilowatts. _Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section 20.6 Electric Hazards and the Human Body_